I want to drill through a 1" thick piece of balsa for my fuel fill and need a 5/8" hole. My drills are all 3/8" drives. I can't find a drill thats 5/8" unless it has a 1/2" drive. Help me out on this!

Barry

Good, sharp, Forstner bit, preferably in a drill press.

I use Forstner bits for drilling larger holes through balsa.

Mark

I'd try a forstner bit, or maybe use a spade bit, but since balsa is very soft I'd sandwich the balsa between two pieces of ply or scrap pine etc. Since the balsa is very soft it would tend to tear out very easily unless supported on both sides

bhady.

You can get a whole set of Forstner bits at Menards for around 30 bucks. They are good enough for balsa work. (Or you can buy just one)

Spad bits don't work so well on balsa, It's too soft.

A spade bit with spurs was very effective when cutting thru a large number of ribs. I wouldn't mess with one unless it has sharp spurs. Also, use two pieces of sacrificial wood - one on each side - to eliminate splintering.

May have to check out those Forstner bits - love to have an excuse for more tools

Been using the Forstners for years and they are great. I have an inexpensive set from 1/4-1" and they all fit a 1/4" chuck.

Hey Augie - have to make any "high altitude" adjustments when using those Forstners?

Is the Forstner bit the one pictured above. Because I used that to make lightening holes in the ribs and wasn't impressed with the result.

Thanks for the replies,

Barry

No, that is a spade bit.

This: http://www.rockler.com/product.cfm?p...lter=forestner is a Forstner bit.

Even though balsa is soft it requires a sharp tool to cut it cleanly. The better one you get, the happier you will be.

I use a brass tube for making holes in balsa. Sharpen the inside of one end of the tube with an exacto knife. Drill out 1/8" deep at a time, cleaning the tube every 1/8"

Kinda hard to chuck 5/8" brass tube into a 3/8" drill chuck....

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You can make yourself an entire set of balsa bits using brass tubes. I use dowel rods inside and turn or sand one end down to fit my drill press chuck. Simple, cheap and works great.
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There are many ways:
- reduce the dia at the chuck end of the tube by using wooden dowels
- or Solder progressively smaller dia concentric tubes inside each other.
- or buy a chuck that accepts larger bits.
- or just do it by hand, balsa is soft.

BTW works great on foam too.

Read section 1.3 on my how to webpage. It describes foam but the same works on balsa too

http://www.wowplanes.com/How_to.htm

I often use the metal tube idea. It also helps to cut a couple notches (V shaped) in the end of the tube to make it easier to pop out the waste material trapped in the tube. I've also used some small hole saws quite effectively.

Forstner bits MUST be sharpened to work well. With a regular drill bit you can get away with a pretty dull edge in harder woods, not so with a Forstner bit, and even with a sharp one if you use it on soft balsa it won't work well.

The picture below is an f-hole cutter, for cutting the circular part of an f-hole on a violin, cello or other stringed instrument. I know not everyone wants to buy a set of these, but it would be very easy to make something that works just a well on balsa. The one pictured has a variety of different size cutters that thread on the handle.

Drill a center hole in a dowel then epoxy it into a brass tube about 1" from the end. Cut the end of the brass tube like the f-hole cutter then put a piece of music wire 1/8"-3/16" into the hole in the dowel. You could make a couple different sizes. To use it, drill a pilot hole the size of the music wire, insert the music wire and twist. The holes it makes are excellent, clean and accurate.

These are all great ideas - many of which I've done in the past, some new to me. Most of them reflect the "craftsman" approach, but neglect that the OP (probably) isn't that type of builder - or he wouldn't need to ask in the first place.

Not many new builders have 5/8" brass tube on hand - heck, many hobby shops don't, either. The OP wants to drill a 5/8" hole through 1" thick balsa. He can stop in at nearly any hardware/home improvement store and get a SHARP forstner bit for less than 10 dollars and be done with it. These other suggestions won't save him substantial money (if any - priced brass tubing lately?) and will cost him time.

Balsa is not foam. TRY sharpening a piece of 5/8" brass tubing and twisting it through a piece of 1" thick balsa by hand - across the grain, not with it. I once did a 3/8" hole in a 1/2" thick block that way - NEVER AGAIN.

You can make yourself an entire set of balsa bits using brass tubes. I use dowel rods inside and turn or sand one end down to fit my drill press chuck. Simple, cheap and works great.
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No, it isn't hard at all to chuck up the brass tube. As this responder has found out, hardwood dowels make a simple stem. Epoxy in place and voila. For balsa, I've filed a saw tooth pattern on the edge of the tube.

Fostner bits are possibly simpler and readily available at hardware stores, so that a great approach. But in a pinch, when you need something right now, you can create the tool yourself

Use a Forstner bit definately. If you start with a new one, balsa will not dull it much. Also, drilla small pilot hole first, then the forstner eill follow it. Do not drill all the way through. Flip your pice over and finish from the other side. This will eliminate tear out.

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I've actually used a regular leather punch with good results. Obviously its for sheeting.. and for smaller holes... But pretty handy.

Otherwise Just a good set of bits. Never forcing it through the wood. And always having some scrap behind it so the bit doesn't rip up the balsa.

I bought a 5/8" Forstner bit today and the hole it made was very nicely done. I was practicing on a scrap but will drill the fuse turtle deck tomorrow.

Thank you for the replies and the Forstner idea, I will use different sizes for lightning the outer wing panel ribs,

Barry

I've used the brass tube technique in many places. You really don't even need a drill, as long as your tube is sharp. In my experience a sharpened brass tube will make a hole about 10times cleaner than any drill bit too. Its a very precise hole. I've done holes up to 1/2"... A tube will not leave any jagged edges, will not tear the wood as it exits, none of that.... and.... the coolest thing... you can angle your hole as you need... as in push-rod exits... very very cleanly. Most everyone has a tube sitting around in a junk space... I think those who haven't tried it really should... you'd be amazed. Be sure to sharpen the inside with an X-acto, just stick the blade inside, spin the tube so your cutting the inside... it doesn't hurt to hit the outside with a little sandpaper, but thats really not necessary. Find a scrap piece of balsa and check it out.. then cut some angle holes too... I wouldn't be without my tubes for making holes in balsa... you can get some serious angles too.. I have found with the bigger diameter holes.. as someone mentioned.... just dremel some teeth into your tube... just put the tube to the wood and spin in.. in thin balsa, you can make a hole quicker then you can grab a drill... in thicker balsa.. you can make a hole quicker then you can set-up your drill... I'm obviouly a fan of tube-cutting balsa...its one of the best tricks I've learned over the years.